Yes, they have done a lot for her and she never ever should have lied to them abt Sushma. But still, I think she is not getting the space she requires at times. Jyoti needs to make a decision, because its obvious she can't balance life b/w her maayka and sasural.
There are only a few options:
Option 1: Go tell her entire family that she has a sis named Sushma, Brij story, etc. And that she needs space sometimes because her family is dependant on her because of her father's handicap. And that she will not forget her duties at home, but that she cant ignore her maayka either.
Option 2: Keep up her lies and ignore her maayka's problems.
Obviously since option number 2 is practically impossible, Jyoti needs to come clean with the truth. She needs to lay everything in front of the Vashishts and then tell them what she wants. If not, things are only going to get worse for her.